A can do a piece of work in certain number of days,while B takes three days more than A to complete the same work. Working together, A and B can complete the work in two days. How many days does B take to complete the work?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 6.
Let the number of days taken by A be x.
Number of days taken by B = x + 3
Work of A and B together for 1 day = 1/x + 1/(x + 3)
Given, 1/x + 1/(x + 3) = 1/2
⇒ 2(x + 3) + 2x = x2 + 3x
⇒ x2 - x - 6 = 0
⇒ (x -3)(x + 2) = 0
⇒ x = 3; -2 (Not possible)
Now, time taken by B = x + 3
⇒ 3 + 3 = 6 days